IP stands for Ingress Protection: But what is it?
IP or Ingress Protection ratings are defined in international standard EN 60529 (British BS EN 60529:1992, European IEC 60509:1989). They are used to define levels of sealing effectiveness of electrical enclosures and other equipment against intrusion from foreign bodies (tools, dirt etc) and moisture.
The numbers that follow IP each have a specific meaning, as outlined in the table below. The first indicates the degree of protection (of people) from moving parts, as well as the protection of enclosed equipment from foreign bodies. The second defines the protection level that the enclosure enjoys from various forms of moisture (drips, sprays, submersion etc).
More recently a new test, IPX9 has been introduced, which is defined as protection against close-range high pressure, high temperature spray downs - often used for cleaning purposes.